Client

Maryland Department of Transportation State Highway Administration (MDOT SHA)

Key Services

  • Geomorphic Stream Assessments
  • Stream Restoration Design
  • Wetland Enhancement and Creation
  • Permitting Support

Project Details

The Maryland SHA, in conjunction with the Federal Highway Administration (FHWA) and the US Army Corps of Engineers (USACE), conducted a Project Planning Study along the MD 175 Corridor through Odenton and Fort Meade in Anne Arundel County, MD.  The purpose of the MD 175 Corridor Project is to improve the existing capacity, traffic operations, intermodal connectivity, and vehicular and pedestrian safety of MD 175, while supporting existing and planned development in the area

Coastal Resources, Inc. (CRI) conducted a geomorphic assessment at two perennial streams (WUS S1 & S2) and one intermittent stream (WUS S25).  CRI conducted restoration design at one of the perennial stream channels (WUS S2) and the intermittent stream channel (WUS S25) located in or adjacent to the MD 175/295 interchange as on-site mitigation for stream impacts resulting from proposed MD 175 Corridor Project.  One of the streams is located on National Park Service (NPS) property.

The mitigation proposed for impacts to WUS S2 includes removing the concrete lining and relocating approximately 132 linear feet of WUS S2 to the north in order to provide a natural channel conveyance to a new culvert that crosses under MD 175.  This on-site relocation of WUS S2 will minimize the amount of stream channel that would otherwise be piped underneath MD 175.  Additionally, within the area of pavement removal resulting from realignment of the MD 295 northeast outer ramp, native vegetation and trees will be planted to establish a 25 to 30-foot buffer along the grass swale segment of WUS S2.

The mitigation proposed for impacts to WUS S25 includes removing the concrete channel carrying WUS S25 and replacing it with a 183 linear foot natural channel with earthen bed and banks.  Three riffle grade controls will be installed into the new channel for grade control as well as creation of natural pool-riffle streambed morphology.  The riffle grade control stone mix was sized to withstand the maximum shear stress predicted from the hydraulic variables and will be keyed into the stream bed and banks to prevent flanking or undermining.  To promote the stability of the proposed streambanks, live stakes and tubelings will be planted along the streambanks.  Areas where trees are removed will be replanted with native, shade tolerant trees and shrubs.

Avoidance and minimization of impacts to trees is an important component of the restoration design process.  The wooded quality of the Baltimore-Washington Parkway corridor is intrinsic to its natural setting.  The rehabilitation of the stream located on the NPS property will have the potential for negative effects from the loss of the mid-successional trees and vegetation that comprise the natural setting of the Parkway. Therefore, design of the proposed action included measures to minimize vegetation loss and protect and replant impacted trees onsite.

CRI also coordinated with the roadway designer to provide design plans, specifications, estimate, and a report narrative for the SHA Design Milestones (30%, 65%, 90%, and 100% PSE). CRI worked with the engineer to design the phased erosion and sediment control plan for the overlapping roadway and stream restoration design.  CRI provided permitting support for the coordination with NPS. Meetings and site visits with NPS and submission to the NPS Stream Restoration Reviewer was coordinated by CRI and SHA.